Control system and apparatus



Tro/Iey H. H. JOHNSTON.

CONTROL SYSTEM AND APPARATUS.

APPLICATION FILED MAY 23, m9.

Patented Nov. 28, 1922.

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ATTORNEY Patented Nov. 28, 1922.

UNITED STATES I a 1,437,107 PATENT OFFICE.

HOWARD H. JOHNSTON, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

CONTROL SYSTEM AND APPARATUS.

Application filed May 23,

To all whom it may concern:

Be it known that I, Howlinn ll. JoHN- sroN, a citizen of the United States, and. a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania. have invented a new and useful Improve ment in Control Systems and Apparatus, of which the following is a specification.

My invention relates to control systems and apparatus for dynamo-electric machines and particularly to automatic control systems involving the use of the familiar limit switch and overload trip devices.

One object of my invention is to provide a single relay device having the double function of both a limit s itch and an overload trip, the parts being so relateiil that a single actuating coil may be utilized for independently performing the two functions, that is to say, under dilferent operating conditions corresponding to the normal maximum, and to an overload, current.

Another object of my invention. is to provide a combined relay device of the aboveindicated character having a plurality of actuating coils so i-onnected to the load circuit to be controlled as to effect similar actuations of the device during the occurrence of a predetermined load-circuit current or of a substantial doubling thereof; or, in other words. I provide a single relay device for affording the same limit-switch operation during the series-parallel connections of a plurality of electric motors, for example, and also the same degree of overload. protection during both series and parallel operation of the motors.

Other specific objects of my invention Will become evident from the follow detailed description. taken in conjunction w the accompanying drawing. wherein .l-ig. 1 a view in elevation of combined relay device ccnstru::ted in accordance ith the present invention; Fig. 2 is a diagrammatic view of a series-parallel system of control embodying the relay device that is shown in Fig. 1; and Fig.3 is a chart. representing various flux values during different operating conditions of the relay device.

Referring to Fig. 1, the structure shown comprises a series or current coil 1; a shunt or voltage coil 2 alined therewith; concentrically related stationary and movable core members 3 and 4, respectively; a plurality of movable contact members or discs 5 and 1919. Serial No. 299,133.

6, respectively corresponding to the limitswitch and to the overload-trip functions of the device, both of the contact discs being loosely mounted upon a centrally located rod or core member 7 that extends through both the movable and the stationary core members 3 and 4, respectively; and a movable armature device 8 for a purpose to be set forth.

The seriescoil 1 comprises a plurality of convolutions of strap conductor of suitable current-carrying capacity, while the shunt coil 2 may be formed of relatively small cross-section wire, since only a relatively low current passes therethrough.

The stationary core member 3 is located substantially within the series coil 1, while the movable core member or plunger 4 is substantially surrounded by the shunt coil a suitable length of air-gap being left be tween the two core members, in accordance with a familiar practise. Also, a suitable spring 1c, located in the air-gap, serves to bias the plunger 4 to the illustrated upper position.

The contact disc 5 is resiliently associated with the concentrically related rod 7 and movable core 4 by means of a coil spring 12, one end of which engages the upper face of the core, the spring acting to force the disc 5 upwardly towards the illustrated posiion of engagement with a pin 13 in the rod 7, and alsotowards ,a posit-ion of electrical contactwith a set of stationary terminals 14.- and 15, which are connected in the customary circuit that is controlled by a limit switch or current relay in automatic control systems for railway motors, and the like. A centering sleeve 12c moves with the plunger 4 to limit the upward travel thereof.

The contract disc (3, corresponding to the overloznl-trip function of the relay device, likewise resiliently associated with the rod 7 through the agency of a helical spring 16. the upper end of which bears against a pin 17 in the rod 7 to bias the contact disc downwardly towards a position of engagement with another pin 18 and also towards a position of electrical contact with a plurality of stationary contact terminals 19 and 20, which are connected in circuit in accordance with the familiar practice rela tive to overload-trip devices.

As previously stated, the rod 7 extends through both the stationary and the movable core members 3 and a respectively, being journaled at its upper end in a suitable strap or bracket 21, the lower end of the rotl projecting slightly below the stationary core member 3 and resting upon an oscillatable armature or magnetizable member 22, one end of which is pivotally mounted upon a suitable pin 23. The entire armature de vice 8, including the armature proper 22 and a latch or detent 24, is preferably of the well-known form that is customarily associate l with overloap-trip relay devices. See for BXttli'lPlB, Patent q t1,312,757, granted. Aug. 12, 1919. Without complete illustration, it will be understood that the latch 2s normally holds the armature 22 in the illustrated position and is itself biased downwardly to prevent the return of the armature 22 to the illustrated position after it has been attracted upwardly by the core members to its overload position. Preferably, the familiar electrically-c-ontrolled re-setting device is also associated with the latch 24 to return the latch and the armature to the illustrated position whenever the motorman throws a controlling switch. Since the resetting feature is well-known in the art, and, moreover, is not essential to the operation of my present invention, I. have not deemed it necessary to completely illustrate this device.

The mechanical operation of my combined relay device may be set forth as follows: Assuming first that the series coil 1 alone is energized, the movable core member a is attracted downwardly, to allow the contact disc 5 to drop from its position of engagement with the stationary contact terminals 14: and 15, whenever a predetermined value of current, corresponding to the desired normal maximum operating value in the loadcircuit, traverses the series coil 1. As soon as the current decreases to a certain value, the movable core or plunger l is returned by the spring a to its illustrated upper posi t-ion to resiliently actuate the contact disc 5 to the position of engagement with the contact terminals 14 and 15. In this way, the familiar intermittent energization of the desired auxiliary governing circuits in an automatic system of control, corresponding'to the well-lvnown limit-switch or current-relay action, is provided by the illustrated relay device.

During such operation, the contact disc 6, corresponding to the overload-trip function, remains stationary in its illustrated contactmaking position. However, if the current in the series coil 1 attains an undesirably high or overload value, the armature 22 is attracted upwardly to a position of direct engagement with the lower face of the stationary core member 3 to carry the rod 7 upwardly to a sufiicient extent to lift the contact disc 6 out of engagement with the terminals 19 and 20. In this way, the customary governing circuit corresponding to overload-trip protection is opened at any desired main-circuit current value, dependent upon the adjustment of the armature device 8, as will be understood by those skilled in the art. During the overload operation just described, the limit-switch disc 5 is also drawn down from its illustrated upper position by reason of the previously described action of the core l. However, this action is of no significance, since the motor circuits are opened by means of the contact disk 6.

Consequently, the limit-switch and overload-trip functions of the relay device are accomplished entirely independently of each other, and, moreover, employ different magnetizable members, viz, the movable core 4; and the armature 22, for effecting the desired results.

Referring to Fig. 2, the system shown is of a familiar type for controlling a plurality of railway motors and comprises, essentially, suitable supply-circuit conductors such Trolley and Ground; a plurality of dynamo electric machines, respectively having commutatontype armatures A1 and A2 and series field windings F1 and F2; an accelerating resistor 80; and a plurality of switches: LS for governing theconnection of the motors to the supply circuit, B1, B2 and R3 for short-circuiting different sections of the ac celerating resistor 30, S corresponding to series connection of the motors and P and G corresponding to parallel relation of the m0- tors. I

My combined relay device is illustrated diagrammatically in Fig. 2, the series actuating coil 1 being continuously connected in series relation with the motor circuit to receive the full current thereof, while the shunt coil 2 is connected in a circuit that is established from the Trolley through conductor 31, interlock P-in of the parallel-connecting switch P, conductor actuating coil 2, adjustable resistor 33, and thence to Ground. In other words, the series coil 1 registers the current flowing through the motor circuit, whereas the shunt coil 2 measures the voltage across the motor circuit.

Inasmuch as an auxiliary governing system for the various switches shown in Fig. 2 may be readily devised by those skilled in the art, in accordance with well-known operating principles, I have not deemed it necessary to illustrate or describe such an auxiliary system. Moreover, since the ordinary limit-switch and overload-trip functions are well-known and the connections of the separate relay devices that are normally employed for these two purposes are also familiar, I have not considered it necessary to illustrate in detail such. connections of the contact discs 5 and 6,, which, as previously stated, correspond in every way to the customary limit-switch and overload-trip operations, respectively.

Assuming that it is desired to effect series operation of the illustrated motors, the switches LS and S are closed to establish a circuit from the Trolley through the series actuating coil 1 of my relay device, line switch LS, the entire accelerating resistor 30, armature A1, field winding Fl, switch S, armature A2, and field winding F2 to Ground. Thus the series actuating coil 1 receives the full current traversing the motors, whereas the shunt actuating coil 2 is de-energized by reason of the open condition of the switch P and, therefore, of the circuit for the actuating coil.

It will be understood that the resistor short-circuiting switches R1, R2 and R3 may be successively closed, in acordance with the operation of the actuating coil 1 and the contact disc 5 of my relay device, as previously set forth, to gradually short-circuit the accelerating resistor 30 and accelerate the motors to full series relation.

The familiar shunting transition of the motors, involving the closure of switch 1, the opening of switch S and the closure of switch G, may then be effected to thereby connect the motors in parallel relation, as will be evident Without a detailed tracing of the circuits. Consequently, the combined current that traverses the two motors, equalling substantially twice the amount flowing through the motor circuit during series operation, also traverses the series actuating coil 1 of my relay device. For this reason, the limit-switch setting of the relay device Would be substantially doubled over that employed during series acceleration and desired during parallel operation also, were it not for the additional provision that I make. However, by utilizing the shunt coil 2 during such parallel operation and connecting it differentially with respect to the series-actuating coil 1., the same limit setting, and likewise the same degree of overload protection, is obtained during both series and parallel connection of the motors, irrespective of the substantial. doubling of current in the series-actuating coil 1.

The energization of the shunt coil 2 is automatically effected upon the closure of the parallel-connecting switch P by reason of the formation of the previously traced. circuit through the coil 2 and the interlock P-in. By mechanically adjusting the armature 22 of the relay device in the usual manner, before the car is put into service, to provide the desired degree of overload protection, and by then manipulating the resistor 33 to a corresponding condition, the actuating coils 1 and 2 of the relay device, by reason of their differential action, will provide the same degree of magnetic attraction or the same amount of effective flux during both the series and the parallel operation of the motors.

This fact is graphically shown in Fig. 3, wherein the vector ,6, corresponds to the average flux emitted by the series-actuating coil 1 during series operation of the motors, or, in other words, the vector 125 is a measure of the average magnetic attraction upon the movable core 4 of the relay device. A substantially equal value of flux is created by the series coil 1 during the transitional period, while an equal and opposite amount of flux, represented by the vector a is produced by the shunt coil 2 during the transition of the motors from series to parallel relation, before the parallel connection is actually completed.

The normal or average flux conditions in the relay device during such parallel operation are represented by the correspondingly designated vectors in ig. 3, 6 representing the substantially doubled flux created in the series coil 1 by reason of the parallel connection of the motors, while 95, indicates the opposing or differential flux that is set up by the shunt coil 2. Consequently, the effective flux that acts upon the movable core member 4 is substantially equal to the flux 56,, which represents the total flux created by the relay device during series operation of the motors.

The next succeeding set of vectors in Fig. 3 shows a vector o greater than the sum of the vectors ,6, and o to represent the increased total flux that is produced in the relay device whenever the limit-switch portion thereof functions to effect the operation of a resistor short-circuiting switch such as R1, which, of course, causes a temporary increase of current in the motor circuit. The vector v5 therefore, corresponds to the value of current necessary to effect the previously described limit-switch action of my relay device.

The next set of vectors in Fig. 3 includes a vector (6,, longer than the vector 6,, and corresponding to the amount of current that is required to traverse the series actuating coil 1 to cause the armature 22 to assume its upper position and thus lift the contact disc 6, whereby the desired overload protection of the motors is provided.

The last vector a corresponds to the effective fiux produced by the relay device under overload. conditions. As indicated by the accompanying legends, the vector 56,, is equal to the sum of the vectors a, and 6 or to the difference of the vectors 6 and 23,, plus the vector o Since the vectorial sum of o and v5, represents the effective mag 'netic attraction exerted by the relay device during parallel operation of the motors, while the vectorial difference of at, and 6 plus the vector e represents that attraction during series connection of the motors,

it follows that substantially the same degree of overload protection is automatically furnished by my relay device during both series and parallel operation. By analogy, it. also follows that the same average current is maintained by the limit-switch action of my relay device under both conditions of motor operation.

I do not wish to be restricted to the specific structural details, circuit connections or arrangement of parts herein set forth, as various modifications thereof may be effected Without departing from the spirit and scope of my invention, I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. In a system of control, the combination with a load circuit, of a relay device having a plurality of actuating coils having materially diflerent operating characteristics and connected for different operating periods to said load circuit to effect similar actuations of the device during the occurrence of a predetermined load-circuit current or of a substantial doubling thereof.

2. In a system of control, the combination with a load circuit, of a relay device having a plurality of actuating coils respectively connected in continuous series relation with said load circuit and in shunt relation thereto under relatively high current conditions therein, and an armature for the relay device, the coils being differentially related to create the same magnetic attraction for said armature during the traversal of a predetermined load current or of a substantial doubling thereof.

3. In a system of control, the combination with a plurality of dynamo-electric machines and means including a plurality of switches for effecting series-parallel opera tion of said machines, of an overload relay device for governing the machine circuit and having a plurality of actuating coils respectively connected in continuous series relation with the machine circuit, and in shunt relation thereto when one of the parallel-connecting switches is closed, and an armature for the relay device, the coils be ing differentially related to create the same magnetic attraction for said armature and degree of overload protection for the machines during both series and parallel operation thereof.

4:. In a system of control, the combination with a load circuit, of a single relay device memo? having the double function of limit switch and overload trip comprising an actuating coil and a plurality of magnetizable members independently actuable thereby at different current values in the coil.

5. In a system of control, the combination with a load circuit, of a single relay device having the double function of limit switch and overload trip comprising an actuating coil, a plurality of magnetizable members respectively located within and without said coil, and contact members corresponding to the limit-switch and to the overload-trip functions actuated by the respective magnetizable members.

I 6. In a system of control, the combination with a plurality of dynamo-electric machines, and means for effecting series-parallel operation thereof, of a single relay device having the double function of limit switch and overload trip comprising an actuating coil connected in series relation with the machines, a core member located within said coil, an armature located below said coil, a plurality of contact discs corresponding to the limit switch and to the overload-trip functions actuated by said core member and by said armature respectively, and means for causing the relay device to produce substantially the same effective flux during parallel operation of the machines as said actuating coil alone produces during series operation.

7. In a system of control, the combination with a plurality of dynamo-electric machines, and means for effecting series-parallel operation thereof, of a single relay device having the double function of limit switch and overload trip comprising an actuating coil connected in series relation with the machines, a core member located within said coil, an armature located below said coil, a plurality of contact discs corresponding to the limit switch and to the overload-trip functions actuated by said core member and by said armature respectively, and a second actuating coil connected in shunt relation to said machines during parallel operation thereof to produce a differential flux equal to substantially one-half of the contemporaneous flux created by the series-connected actuating coil.

In testimony whereof, I have hereunto subscribed my name this 16th day of May 1919.

HO WARD H. JOHNSTON. 

